This invention relates to an automatic coating apparatus which is equipped with a cartridge gripper for replaceably and selectively mounting and dismantling paint cartridges of various colors on the coating apparatus.
Generally, for coating object such as vehicle bodies, for example, rotary atomizing head type coating apparatus have been in wide use. Lately, coating apparatus of this sort are increasingly required to meet demands for reductions of the amounts of paint and solvent to be discarded at the time of color changes and for capability of coping with a large number of paint colors.
There has been known a rotary atomizing head type coating apparatus which is so arranged as to reduce the amounts of discarding paint and solvent and which can cope with an increased number of paint colors, for example, from Japanese Laid-Open Patent Publication No. H8-229446. This rotary atomizing head type coating apparatus uses paint cartridges which are filled with different paint colors and adapted to be selectively and replaceably mounted on the coating apparatus in the course of a coating operation on vehicle bodies.
Regarding coating operations on vehicle bodies or the like, there has also been known automatic coating apparatus (e.g. from International Gazette WO97/34707) which is arranged to perform a coating operation automatically according to programmed procedures. This automatic coating apparatus is comprised of a working mechanism such as a coating robot which is provided in a coating area, a coating machine which is mounted on the working mechanism and provided with a rotary atomizing head adapted to be put in high speed rotation by an air motor for atomizing paint into minute particles, a number of paint cartridges which are filled with paint of different colors and adapted to be replaceably mounted on the coating machine, and a cartridge gripper which is arranged to pick up a replenished paint cartridge and mount it on the coating apparatus in place of an empty paint cartridge.
In the case of the prior art automatic coating apparatus which is arranged as described above, paint is supplied from the cartridge to the rotary atomizing head, which is put in high speed rotation by the air motor, and thereby sprayed toward a coating object. At this time, the working mechanism is put in operation to move the coating apparatus along contours of coating surfaces of a coating object.
When changing the paint color, the working mechanism is moved to bring the paint cartridge on the coating apparatus to a position in the proximity of the cartridge gripper. Then, the cartridge gripper is operated to remove the consumed or empty paint cartridge from the coating apparatus and to mount thereon a fresh paint cartridge which is filled with a different paint color.
The above-mentioned prior art automatic coating apparatus is arranged to mount and dismantle paint cartridges on and from the coating apparatus by gripping actions of the cartridge gripper. However, generally cartridge grippers of this sort could become inoperative due to troubles of gripping parts or components, thereby presumably failing to grip a paint cartridge in a satisfactory manner. In the case of the prior art automatic coating apparatus, a coating operation proceeds automatically according to a preset coating program irrespective of a failure in dismantling a used paint cartridge from the coating apparatus or in mounting a fresh paint cartridge on the coating apparatus. Therefore, in such a case, it is difficult to form coatings of appropriate quality on coating object, not to mention deteriorations in yield and productivity.
Further, the automatic coating apparatus is arranged to replace a used empty paint cartridge on the coating apparatus by a fresh paint cartridge which is replenished with paint. However, in the event of a trouble occurring to a cartridge replenishing apparatus, one may face a situation where a replacing cartridge is not replenished with paint at all. Since the amount of paint within a replenished cartridge is not visible from outside, it is only after a coating operation has actually started that a judgement can be made as to whether or not a freshly mounted paint cartridge is replenished with paint to a sufficient degree.
For this reason, it is likely for the automatic coating apparatus as in the above-mentioned prior art to experience difficult situations in which paint in a cartridge becomes prematurely deficient in the course of a coating operation, and as a result often suffer from coating defects.
In an attempt to solve the above-mentioned problems of the prior art, the present invention contemplates to provide an automatic coating apparatus which can attain higher yield and productivity in coating by precluding malfunctioning of a cartridge gripper or its components and at the same time detecting a non-replenished or deficiently replenished paint cartridge beforehand.
More particularly, this invention concerns an automatic coating apparatus of the type which is basically comprised of a working mechanism located in a coating work area, a coating apparatus mounted on said working mechanism and having a rotary atomizing head to be put in high speed rotation by an air motor for atomizing paint into minute particles, a number of paint cartridges of different colors each adapted to be replaceably and selectively mounted on the coating apparatus, and a cartridge gripper unit adapted to grip a replenished paint cartridge to replace a used empty paint cartridge on the coating apparatus.
In order to solve the above-mentioned problems, according to the present invention, the cartridge gripper unit is arranged to comprise a gripper member adapted to grip and pick up one of the paint cartridges, a grip detection means adapted to detect whether or not the paint cartridge is securely gripped by the gripper member, and a replenishment level detection means adapted to detect whether or not the paint cartridge is replenished with paint to a predetermined degree.
With the arrangements just described, when the paint cartridge is gripped by the gripper member, the grip condition of the gripper member which holds the paint cartridge is checked out by the grip detection means to detect beforehand incomplete grip conditions which might have resulted from malfunctioning of the gripper member. At the same time, a replenished paint level in the gripped paint cartridge is checked out by the replenishment level detection means to sort out a non-replenished or deficiently replenished paint cartridge if any.
In this instance, the gripper member to be used in the present invention can be comprised of a reciprocating actuator, and a plural number of gripper claws connected to the reciprocating actuator and thereby moved to grip or release the paint cartridge, and the grip detection means is constituted by a switch adapted to detect displacement of the reciprocating actuator.
With the arrangements just described, the gripper member is arranged to grip the paint cartridge between gripper claws which are moved toward and away from each other by reciprocating movements of the reciprocating actuator. At the time of gripping the paint cartridge, location of the gripper claws in a predetermined gripping position is detected by the grip detector switch from a displacement distance of the reciprocating actuator.
Further, the gripper member to be used in the present invention is preferably comprised of a reciprocating actuator, and a plural number of gripper claws connected to the reciprocating actuator and thereby closed or opened to grip or release the paint cartridge, and the grip detection means is constituted by a grip position detector switch adapted to detect displacement of the reciprocating actuator to a predetermined cartridge gripping position, and a release position detector switch adapted to detect displacement of the reciprocating actuator to a predetermined gripper claw opening position.
With the arrangements just described, since under normal operation conditions the displacement (reciprocating movement) of the reciprocating actuator comes to a stop at a predetermined position at the time of gripping a paint cartridge between the gripper claws, the grip position detector switch can detect the grip condition from the displacement of the reciprocating actuator to the predetermined gripping position. On the other hand, since the displacement (reciprocating movement) of the reciprocating actuator also comes to a stop at a predetermined gripper claw opening position, the open position detector switch can detect an open state of the gripper claws from the displacement of the reciprocating actuator to the predetermined claw opening position. The gripper claws are abutted against each other in case the displacement of the reciprocating actuator is detected by neither the grip position detector switch nor the open position detection switch.
On the other hand, the paint cartridge to be used in the present invention can be comprised of a container, a feed tube extended out from a fore end of the container, and a movable partition wall provided internally of the container to divide same into a paint reservoir chamber in communication with the feed tube and an extruding liquid chamber connected to a paint extruding liquid supply, said replenishment level detection means is constituted by a detector switch adapted to detect displacement of said movable partition wall when said container is replenished with paint.
With the arrangements just described, upon replenishing paint into the paint reservoir chamber within the container, the movable partition wall is displaced according to the amount of replenished paint. Consequently, when a replenished paint cartridge is gripped between the gripper claws, the replenishment level detector switch can detect the replenished paint level from a displacement distance of the movable partition wall.
Further, the paint cartridge to be used in the present invention is preferably comprised of a container formed of a non-magnetic material and closed on the side of a base end thereof, a feed tube extended out from a fore end of the container, a movable partition wall provided internally of the container to divide same into a paint reservoir chamber in communication with the feed tube and an extruding liquid chamber connected to a paint extruding liquid supply, a core member of a magnetic material provided at the base end of the container, and a permanent magnet provided on the movable partition wall in a confronting position relative to the core member, and the replenishment level detector means is constituted by a magneto-sensitive switch adapted to detect the permanent magnet when moved to the proximity of the core member.
With the arrangements just described, upon replenishing paint into the paint reservoir chamber within the container, the movable partition wall is pushed toward the base end of the container in proportion to the amount of replenished paint, and the permanent magnet on the movable partition wall is brought to the proximity of the core member at the end of a replenishing operation. Therefore, when a container of a replenished cartridge is gripped between the gripper claws, the replenishment level detector switch can detect the permanent magnet through the core member if the paint cartridge is replenished to a predetermined level. On the other hand, in case the container is not replenished with a predetermined amount of paint, the permanent magnet is not detected by the replenishment level detector switch in its proximity.
According to the present invention, the movable partition wall may be constituted by a piston which is slidably fitted in the container for axial sliding movements therein.
Alternatively, according to the present invention, the movable partition wall may be constituted by a bellows tube which is contractibly expansible in the container.